As usual, it's possible to create a script that will break if $$ is modified, but the point is moot as that script would not be making any sense, I don't see the point in not fixing it.
As long as no one can see an issue with backwards compatibility, the change will be in the next beta.
While I understand that $chan is not set 'by' the on input event, but that it is 'by' the on text event (if applicable), I don't understand why "there is no way to set $chan correctly".
That's because you can't see the code the I'm seeing. It's my fault for over-explaining the code. Every once in a while, I like to share how the code works but it can be difficult to explain it. Let's just go with the change and see how things turn out.